Two-stage thermostatic switch mechanism

ABSTRACT

A two-stage thermostatically operated switching mechanism has two toggle switches supported on different levels of an insulator support. The switches have a common terminal member for fixed contacts and movable contacts of the respective switches are operated by overcenter spring mechanisms actuated by a common lever connected with an expansible power element. The overcenter operating mechanism of one switch has an elongated tension spring which is connected with a movable control arm and is caused to shift from one side to the other of dead center by the common lever. The pivot for the contact arm is shiftable towards and from the actuating lever by a screw adjustment.

United States Patent Inventor Gunter II. Fildebraudt Columbus. Ohio [21] AppL No. 6,911 [22] Filed Jan. 29, 1970 [45] Patented Aug. 24, 197] [73} Assignee Ranco Incorporated Columbus, Ohio [54] TWO-STAGE THERMOSTATIC SWITCH MECHANISM 2 Claims, 5 Drawing Figs.

[52] U.S.Cl 337/311,

337/319 [511 lnt.CI ..H0lh37/18, HOIh 37/38, HOlh 37/60 [50] Field ofSearch 337/308, 309,3I0,3Il,3l8, 319

[56] References Cited UNITED STATES PATENTS 3,461,415 8/1969 Dahlgren 337/310 2,991,342 7/l96l Weber et al. 337/308 2,853,583 9/1958 Rauh 337/318 X 2,520,370 3/1950 Offutt 337/308 Primary Examiner-Bernard A. Gilheany Assistant Examiner-Dewitt M. Morgan Attorney-Watts, I-Iofimann, Fisher & Heinke mon lever. The pivot for the contact arm is shiftable towards and from the actuating lever by a screw adjustment.

PATENTEI] M1824 ma l I \l 'IIIIIIII;

INVENTOR GUNTER H. FILDEBRANDT ATTORNEYS TWO-STAGE TI'IERMOSTATIC SWITCH MECHANISM BACKGROUND OF THE INVENTION The present invention relates to thermostatic switches and more particularly to two electric switches which are operated by an expansible-type power element in sequence at predetermined temperatures which may differ.

The present invention provides a compact, inexpensive construction in which two snap acting electric switches are supported on a base at different levels and with the fixed contacts of the two switches having a common terminal member. Both switches are actuated by a common lever which is spring biased against an expansible power element.

Other objects and advantages of the invention will be apparent from the following description of a preferred embodiment thereof, reference being made to the accompanying drawings wherein:

FIG. 1 is a side view in elevation of a two-stage thermostatic switch mechanism embodying the invention;

FIG. 2 is a sectional view of the switch mechanism taken substantially along the line 2-2 of FIG. 1;

FIG. 3 is a sectional view taken substantially along line 3-3 of FIG. 2;

FIG. 4 is a fragmentary sectional view taken substantially along line 44 of FIG. 2; and

FIG. 5 is a sectional view taken substantially along 5-5 of FIG. 2.

Referring to the accompanying drawings which disclose a .preferred form of the invention, a thermostatic control mechanism is shown which comprises two electric switches particularly suitable for use in an air conditioner system to control the circuits of the compressor and an evaporator fan motor in responseto temperature of the space to be cooled by the air conditioner? The air conditioner and fan motor are not shown.

The thermostatic control 10 comprises a housing 11 which may be suitably attached to the air conditioner, for example, with a temperature-adjusting knob'12 accessible to the user of the air conditioner. Two electric switches 13 and 14 are supported in the housing and are actuated in sequence by a thermost atic element 15 in response to the temperature of air entering the air conditioner for cooling. The switch 13 is adapted to be connected in the motor circuit of the air conditioner compressor, and the switch 14 is connected in the motor circuit of the aircirculating fan. The switch 13 is actuated to initiate operation of the compressor when the air temperature to which'the element 15 responds rises to 'a predetermined temperature and breaks the circuit when the temperature is lowered to a predetermined degree. The switch 14is adapted to close the fan circuit as the temperature of the air to which the element 15 responds rises to a predetermined temperature slightly below the temperature at which the switch 13 closes. The switch 14 is opened at a temperature slightly below the temperature at which switch 13 opens.

Referring more specifically to the construction of the thermostaticcontrol 10, the housing 11 comprises a faceplate 17, which has two downwardly turned flanges 20,21 along opposite sides, and two sideplates 22,23 which are attached to the faceplate. The sideplates 22,23 are attached to the plate 17 by conventional means not shown in detail. The side of the housing opposite the plate 17 is formed by an insulating block 24 which is attached to the sideplates by lugs 25 formed adjacent the comers thereof and which closely fit in retaining openings formed in the sideplates. One end of the housing is closed by a plate 26 which comprises a part of the power element 15. The plate 26 is positioned between shoulders formed on the inside of plates 22,23 and in-turned flanges along opposite end edges of the sideplates. The details of the shoulders are unimportant to the understanding of the invention and are not shown. The plate 26 is retained between the shoulders and against the faceplate 17 by lugs 30 projecting from opposite sides of the ends of the insulating block 24.

, The switch 13 comprises two terminal members 31,32 which include bladelike portions which extend through slotlike openings in the block 24 and provide terminal connector means. The terminal member 31 has a shoulder portion 33 which rests against the inner surface 34 of the block 24 and is firmly held thereagainst by stake portions 38 cut from the depending terminal member 31 and forced against the underside of the insulating block. The shoulder portion 33 of terminal 31 has a right-angle part 35 extending laterally therefrom and forming a support for a flexible switch blade 36 and an actuator arm 37. The switch blade 36 and arm 37 are riveted to the part 35 by rivets 40.

The terminal member 32 includes a bridge portion 41, a leg portion 42 and a foot portion 43. The bridge 41 has a switch contact 45 riveted thereto. A downwardly extending terminal blade .46 from the foot portion 43 of terminal 32 extends through an opening in the block 24 and is secured, as by staking, in the opening. The foot portion 43 is thus positioned slightly above a surface 47 of the block 24, which surface extends parallel to the surface 34 but is substantially offset downwardly therefrom, as seen in FIG. 2.

The switch blade 36 has a contact 50 at the free end thereof which is adapted to engage contact 44 and close a circuit between terminals 31 and 32. The blade 36 is snap moved to and from the contact 44 by a toggle mechanism-which is like that disclosed in US. Pat. No. 2,556,981. For more specific details, reference may be had to the patent. The snap or toggle mechanism includes a toggle link 51 having one end pivoted to the edge of a central opening 52 in theswitch blade and the opposite end pivoted to one end of an omega-shaped spring 53. The other end of the spring 53 is pivoted to the right-hand end edge of the opening 52.

The toggle link 51 is shifted from one side to the other of the centerline of the blade 36 and its pivot by the actuator 37. The actuator 37 comprises a generally flat spring member having a rectangular opening 54 through which the toggle link 51 and spring 53 extend. A tongue 55 depends from the actuator 37, as viewed 'in the drawings, and has a rectangular opening or window through which the toggle link extends. The upper and lower edges of the window form spaced stops which limit swinging movements of the link 51 in opposite directions. The edges of the window also transmit movement of the actuator 37 to the link 51 as the actuator oscillates about its pivot. A'

screw 57 is threaded through an opening in the block 24 and forms a pivotal stop to limit downward movement of the toggle link.'The screw 57 is positioned between the tongue 55 and the swinging end of the switch blade 36 so that as the actuator 37 moved downwardly the toggle link 51 is pivoted clockwise about the screw 57. This movement causes the toggle link to swing the end pivoted to the omega spring 53 below thecenterline of the blade 36. The force of the spring on the Iink'then snap moves the switch blade 36 upwardly to closed contact 50 on contact 44. As the actuator 37 moves upwardly the toggle link 51 pivots counterclockwise about the end pivoted to the switch blade 36 and swings the end of the link attached to the spring 53 about the centerline of the blade. The force of the spring then snap moves the blade downwardly to separate con- I tact 50 from contact 44.

The actuator 37 is inherently biased to an upward position and against an insulator 60 which forms a part of a bellows actuated lever 61. Tn lever 61 moves in accordance with changes in temperature, as is described more fully hereinafter.

The switch 14 includes the fixed contact 45 and a terminal member 62. Tn terminal 62 includes a head 63 which is maintained against the surface 47 of the block 24 by stakes 64 through an opening in the block 24. The screw 74 is formed of a dielectric material.

Switch blade 71 is snap moved to and from the contact 45 by a tension spring 75, one end of which is attached to the yoke portion of the switch blade and the opposite end of which is attached to a lug 76 formed on the switch support 66. An opening 77 is formed in the support 66 to accommodate the tension spring 75.

The central portion of the tension spring 75 is adapted to be deflected by a finger 78 which projects from the insulator 60 of the lever 61. As the lever 61 moves to lower the actuator 37 of the switch 13, the finger 78 moves in a direction to deflect the tension spring 75 and cause the force of the spring to shift below the center line of the blade 71. This snaps the blade downwardly to engage contact 72 with contact 45. When the lever 61 and the finger move upwardly the spring 75 returns to its normal position in which the force thereof urges the blade 71 upwardly about its pivot to separate contact 72 from contact 45.

The elevation of the end of the support member 66 to which the switch blade 71 is pivoted can be adjusted by a screw 79. The member 66 is resilient and rests against the end of the screw 79 which is threaded through an opening in the block 24. By turning the screw 79 the position of the pivot for the switch blade71 can be raised or lowered relative to the tension spring 75 and thereby change the positions of the finger 78 at which the switch blade is snapped by the spring.

The lever 61 includes the insulator 60, which is of a generally rectangular form, and a sheet metal arm 81 to which the insulator 60 is attached. The arm 81 is generally rectangular and includes two laterally projecting lugs 82,83 which engage edges of openings 84 formed in the sideplates 22,23, respectively, and which provide relatively friction-free pivots about which the lever. swings. The sides of the arm 81 include flange portions which embrace opposite sides of the insulator 60 and secure the insulator thereto.

The lever 61 includes a leg 85 which engages a post 86 of an expansible wafer-type bellows 90. The diaphragm 90 contains an expansible fluid and is attached to the plate 26. The interior of the bellows is in communication with a capillary tube 93 closed at its remote end. The bellows and tube contain a suitable vapor, the pressure of which increases and decreases in correspondence with increase and decrease in temperature of the coolest portion of the capillary tube. The capillary tube 93 is arranged to be disposed in the airstream of air entering the air-conditioning unit which is controlled by the mechanism 10.

The lever 61 is urged clockwise and against the post 86 by a tension spring 95. As the temperature of the capillary tube increases, the bellows 90 tends to expand and move the lever 61 counterclockwise about its pivot. When the temperature in the capillary tube 93 decreases the bellows 90 tends to collapse and permit lever 61 to move clockwise about its pivot. Thus, the switches 13,14 are operated at temperatures sensed by the capillary tube according to the load impressed on the bellows 90 by the spring 95.

The tension of spring 95 is variable by rotation of the knob 12 from one angular position to the other. The mechanism for adjusting the spring tension comprises a screw 96 which is rotatably supported in a foot portion 97 formed on the 81 and one end of the spring 95 is threaded onto the screw. The opposite end of the spring 95 is attached to the yoke of an adjusting lever 100. The adjusting lever 100 is preferably formed of a stamping having two laterally projecting side legs 101,102 which engage edges of openings 104 in the sideplates 22,23 and form pivots for the lever. The lever 100 includes a finger 105 which extends through an opening in the plate 17 and engages the periphery of a flat cam 106 attached to an adjusting shaft 107 to which the knob 12 is attached. The tension of spring on the lever urges the finger against the cam 106. By rotating the shaft 107 by the knob 12 the cam 106 shifts the finger 105 and consequentl the lever 100 to adjust the tension of the spring 95 on the ever 61. As is well uh derstood in the art, the change in pressure of the lever 61 on the bellows 90 changes the temperature at which the arm 61 is effective to actuate the switches 13 and 14. For example, the range of temperatures at which the switches 13 and 14 are actuated according to the position of knob 12 are determined by setting the screw 96 which properly tensions the spring 95 for a given angular position of the knob. The screw 57 is adjusted to provide for selection of the temperature differentials at which the switch 13 is opened and closed. Adjustments ofthe screws 74 and 79 regulate the temperatures at which the switch 14 is opened and closed.

The construction described provides a compact, inexpensive construction for two-stage thermostatic switches. A feature of the invention includes the convenience of calibrating the switches to be actuated at predetermined temperatures.

I claim:

1. A two-stage switch mechanism comprising a housing having an insulating member forming one wall thereof, said member having first and second adjacent and parallel switchsupporting surfaces on different planes, a conductor member having first and second sections extending across one end portion of said first and second surfaces respectively, a contact member attached to each of said first and second conductor sections, a first snap switch mechanism on said first surface and comprising a contact arm at one end remote from said first section, means including said contact on said first section for limiting movement of the other end of said arm, over center toggle means to snap move said first contact arm to and from the contact on said first section, said toggle means including an actuating member having switch operating movements towards and from said first surface, a second snap switch mechanism including a contact arm extending over said second surface, means pivoting one end of the last-mentioned contact arm remote from said second conductor section so that the opposite end is swingable to and from said contact on said second section, means for limiting swinging movement of said last mentioned contact arm including the last-mentioned contact and an abutment adjustably spaced from said lastmentioned contact, a tension spring attached to the swinging portion of said arm and extending beyond the pivot for said second mentioned contact arm, said tension spring disposed so that normally its center of force is to one side of said pivot for said second-mentioned contact arm and beingdeflectable to the other side of said pivot for said second-mentioned contact arm, means to adjustably space the pivot for said secondmentioned contact arm from said second surface, an operating lever pivoted to said housing and swingable towards and from said surfaces, said lever adapted to move said toggle-actuating member, said lever having a part engageable with said tension spring for deflecting said spring, and pressure means for moving said operating lever.

2. A two-stage switching mechanism as defined in claim 1 further characterized by said means pivoting said second mentioned contact arm comprising a terminal member supported by said insulator member and including an integral'resilient cantilever portion providing a pivot connection at the free end thereof with one end of said second mentioned contact arm, and a screw threaded in an opening through said insulator member and engaged by said cantilever portion, said portion adapted to flex according to the position of said screw for adjusting the position of the pivoted end of said second-mentioned contact arm. 

1. A two-stage switch mechanism comprising a housing having an insulating member forming one wall thereof, said member having first and second adjacent and parallel switch-supporting surfaces on different planes, a conductor member having first and second sections extending across one end portion of said first and second surfaces respectively, a contact member attached to each of said first and second conductor sections, a first snap switch mechanism on said first surface and comprising a contact arm at one end remote from said first section, means including said contact on said first section for limiting movement of the other end of said arm, over center toggle means to snap move said first contact arm to and from the contact on said first section, said toggle means including an actuating member having switch operating movements towards and from said first surface, a second snap switch mechanism including a contact arm extending over said second surface, means pivoting one end of the last-mentioned contact arm remote from said second conductor section so that the opposite end is swingable to and from said contact on said second section, means for limiting swinging movement of said last mentioned contact arm including the last-mentioned contact and an abutment adjustaBly spaced from said last-mentioned contact, a tension spring attached to the swinging portion of said arm and extending beyond the pivot for said second mentioned contact arm, said tension spring disposed so that normally its center of force is to one side of said pivot for said second-mentioned contact arm and being deflectable to the other side of said pivot for said second-mentioned contact arm, means to adjustably space the pivot for said second-mentioned contact arm from said second surface, an operating lever pivoted to said housing and swingable towards and from said surfaces, said lever adapted to move said toggle-actuating member, said lever having a part engageable with said tension spring for deflecting said spring, and pressure means for moving said operating lever.
 2. A two-stage switching mechanism as defined in claim 1 further characterized by said means pivoting said second mentioned contact arm comprising a terminal member supported by said insulator member and including an integral resilient cantilever portion providing a pivot connection at the free end thereof with one end of said second mentioned contact arm, and a screw threaded in an opening through said insulator member and engaged by said cantilever portion, said portion adapted to flex according to the position of said screw for adjusting the position of the pivoted end of said second-mentioned contact arm. 